A transmission is a transmission device that changes power of an engine to required torque according to a speed and transmits the torque.
Vehicles or apparatuses such as excavators and mechanical pumps, which operate using the power generated by the engine, require stronger torque and lower rotation at lower speeds, and require high-speed rotation rather than the torque as a speed increases. The transmission plays such a role.
For example, a general automotive transmission includes shift stages from a first stage to a fifth stage. In first and second-stage gears, a reduction ratio is set to be large so as to exert strong force and in third and fourth-stage gears, a gear ratio is set to a gear ratio similar to the engine speed so as to maintain or accelerate the speed at a medium speed and the high speed. The fifth stage is referred to as an overdrive and has a gear ratio lower than the engine speed for driving at the high speed.
The transmission has a manual method in which a person manually operates a clutch and an automatic method in which a mission is directly shifted in accordance with the speed by hydraulic pressure according to whether the clutch is operated and includes a continuously variable transmission (CVT) which may obtain a continuously variable transmission ratio by using a belt instead of a gear.
In the past, the manual method was mainly used, but due to troublesomeness of an operation method, the automatic transmission or the continuously variable transmission has been mainly used in recent years.
Among them, the automatic transmission has a complicated structure and a high price, especially, the automatic transmission has a high fuel consumption rate compared to the manual method and since the gear ratio of the continuously variable transmission is continuously changed, it is possible to continuously use specific rpm to show the largest force, and as a result, fuel efficiency is improved, but there is a limit in transmitting large force, and as a result, in particular, there is a limitation that the automatic transmission is mainly used for a light-weight vehicle because there is a disadvantage that the power may not normally transmitted at the start or at the low speed and durability is weak.
Therefore, it is required to develop a new compound transmission that can get the advantages of each transmission out of a single-type transmission.
Meanwhile, the transmission is applied even to the excavator or a water pump to perform drilling or pumping of groundwater while rotating a shaft and even in this case, in order to change a pumping rate and change drilling performance, the rpm or torque of the shaft needs to be smoothly varied, a new compound transmission is required.